The present invention relates to a heat storage means, and more particularly to a latent heat storage means for motor vehicle heating systems supplied by engine waste heat, comprising an inner container with a storage core within it, an outer container surrounding the inner container with a clearance with the formation of a preferably evacuated insulating space and two ducts extending through the insulating space, of which one duct serves as a supply duct and of which the other serves as a return duct for a heat vehicle fluid and both are arranged adjacent to the insulating space in such a manner that they have a straight section which is as long as possible.
A heat storage means of this type is described in the European patent application 0 294 500. The duct sections extending upwards and, respectively, downwards serve to for an insulating barrier layer, which is effective during the heat storing phase, in the heat vehicle fluid between the hot fluid present in the heat storage means and the fluid cooling outside the heat storage means so that heat losses, which would reduce the utility of the heat storage means via the ducts passing through the insulating space are prevented.
It is not in all applications, as for instance in private cars, that there is sufficient space available to make it possible to install a heat storage means in such a position as to lead to a duct section which is sufficiently long and/or suitable for the formation of a barrier layer.